/**
 * Created by feifan on 2016/6/5.
 */
module.exports = function (l) {

    var k = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';

    return function (){
        var arr=[];
        var r = ()=>Math.floor(Math.random() * 36);
        for (let i = 1; i < l; i++) {
            arr.push(k.charAt(r()));
        }

        return arr.join('');
    }
};